The invention relates to a pressure sensor having a housing which has a measuring space, having a measuring cell which is supported in the housing by means of a retaining body and bounds the measuring space, and having an electric contact base which is connected to the measuring cell, the measuring space being able to be subjected to pressure via an opening in the housing. The invention furthermore relates to a method for producing a pressure sensor of this type.
To measure the pressure of gases or liquids, the pressure sensor is inserted in a sealing manner into a container holding a gas or a liquid. For this purpose, known pressure sensors have, for example, a connecting piece which is provided with an external thread and by means of which the pressure sensor can be screwed into the container. This connecting piece furthermore has an opening which is designed as a hole and through which the medium which is to be measured passes into a measuring space closed by means of the measuring cell. The measuring cell is supported for this purpose in the housing by means of a retaining body and is sealed from the medium to be measured by a sealing ring. The pressure sensor is contacted via a contact base which is placed onto the retaining body. The contact base protects the contact elements arranged in the interior by means of its sealed connection to the housing, with the result that the pressure sensor, together with its mounting parts, forms a hermetically sealed unit.
Depending on the intended use, the pressure sensor provided in this manner also has to withstand a high pressure. Therefore, according to a known production method, the retaining body, which fixes the measuring cell, is pressed into the housing. The contact base, which consists of an electrically insulating material, generally plastic, is then likewise pressed into the housing and thus encloses the measuring cell in the interior of the housing. For the electrical contact-making, the contact base has contact pins which protrude into the interior of the pressure sensor and are connected to the measuring cell.
In a known embodiment, following the installation, the measuring cell is calibrated. Of disadvantage in this case is that the pressure sensor is inaccurate, the inaccuracy arising over time and resulting from a change in the mechanical clamping ratios. In addition, the outlay on installation of the pressure sensor is high which in particular also makes automation of the installation more difficult.
In another known embodiment, after the retaining body which fixes the measuring cell has been pressed in, the measuring cell is set to the desired values. The contact base is then placed on and likewise pressed in. Of disadvantage in this case is the fact that the subsequent pressing-in of the contact base enables deviations from the desired value set to arise once again.
Furthermore, in the case of both embodiments described, it is disadvantgeous that ageing processes can occur, in particular in the plastic material generally used for the contact base, but also in the retaining body, which ageing processes can lead to a relaxing of the pressing-in force and hence to inaccuracies in the determined measured values. Likewise, differing thermal expansions of the various components influence the measuring accuracy.
In addition, the case of pressure sensors subjected to particularly high stress, axial displacement of the retaining body and the measuring cell supported by said body can occur in the housing. The durably constant measuring accuracy of the measuring cell can therefore be achieved only with a considerable additional outlay.